排序算法之快速排序

// QuickSort.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

#include "iostream"
using namespace std;

//   说明：排序算法 - 快速排序, 通过一趟排序将待排记录分割成独立的两部分，其中一部分记录的关键字比另一部分记录的关键字小，则可分别对这两部分记录继续进行排序，以达到
//   整个序列有序;

int FindPivotIndex(double a[], int low, int high)
{
	double dTemp = a[low];

	while (low < high)
	{
		while (low < high && a[high] > dTemp)
		{
			high--;
		}

		while (low < high && a[low] < dTemp)
		{
			low++;
		}

		swap(a[low], a[high]);
	}

	return low;
}

void QuickSort(double a[], int low, int high)
{
	if (low < high)
	{
		int iIndex = FindPivotIndex(a, low, high);

		QuickSort(a, low, iIndex - 1);
		QuickSort(a, iIndex + 1, high);
	}
}

int _tmain(int argc, _TCHAR* argv[])
{
	double a[] = {2.0, 5.4, 4.0, 8.0, 3.0, 5.0, 1.0, 9.0, 7.0};
	int n = sizeof(a) / sizeof(*a);

	cout<<"排序前：\n";
	for each (double x in a)
	{
		cout<<x<<" ";
	}
	cout<<endl;

	QuickSort(a, 0, n-1);

	cout<<"排序后：\n";
	for each (double x in a)
	{
		cout<<x<<" ";
	}
	cout<<endl;

	return 0;
}